First bath sizing solution for two-bath sizing

Abstract

This invention belongs to the field of surface treatment technology for fiber-reinforced materials in rubber products, and particularly relates to a first bath impregnation solution for a two-bath impregnation method used to enhance the adhesion between synthetic fibers such as polyester and nylon and rubber. The invention comprises a dry component and a wet component, wherein the wet component has a mass ratio of 90%-99% and the dry component has a mass ratio of 1%-10%. The dry component comprises the following components by mass percentage: 50%-75% blocked isocyanate component, 15%-40% epoxy component, 1-5% thioester antioxidant, 1-5% polyfunctional siloxane compound, and 1-5% polyether compound. This invention significantly improves the adhesion and over-sulfurization degradation performance between fibers and rubber by adding thioester antioxidant, polyfunctional siloxane compound, and polyether compound.

Description

Technical Field

[0001] This invention belongs to the field of surface treatment technology for fiber skeleton materials in rubber products, and particularly relates to a first bath impregnation solution for a two-bath impregnation method used to enhance the adhesion performance of synthetic fibers such as polyester and nylon to rubber. Background Technology

[0002] In the rubber products industry, fiber skeleton materials refer to various high-strength fibers or fabrics embedded in the rubber matrix, which mainly play a role in reinforcement, support and shape maintenance. Their adhesion to rubber and the degradation of adhesion during long-term use play a crucial role in the performance and lifespan of rubber products.

[0003] To address the adhesion problem between the reinforcing fiber and rubber, especially for polymer fiber reinforcing materials such as nylon and polyester, the RFL (resorcinol-formaldehyde-latex) impregnation system is currently widely used. This system achieves adhesion by two mechanisms: firstly, the resorcinol-formaldehyde condensate interacts with the polar groups on the fiber surface to form a bond; secondly, the latex cross-links with the rubber to form a bond, thus achieving adhesion between the two cross-sections. Therefore, the reactivity of the fiber surface has a significant impact on the adhesive strength.

[0004] For some reinforcing materials, such as polyester and some polyamides (such as aramid), there is an inherent problem of insufficient interaction with the RFL impregnation system. Therefore, existing technologies generally enhance adhesion by adding a first bath of pre-impregnation, i.e., a two-bath impregnation method. The main components of the first bath in the two-bath impregnation method are epoxy components, blocked isocyanate components, and water. After curing and crosslinking, these components generate more polar functional groups on the fiber surface, which makes the pre-impregnated fibers have a strong interaction force with the components in the RFL system, thereby enhancing the fiber-rubber adhesion.

[0005] For example, Chinese invention patent CN103596779A discloses a rubber-fiber composite that improves tire durability. By pretreating the fiber-coated adhesive composition, the dynamic adhesion of polyester fibers is significantly improved. The adhesive composition mainly involves condensates of resorcinol and formaldehyde, chlorophenol, condensates of resorcinol and formaldehyde, and compounds formed from epoxy cresol formaldehyde resin. However, the chlorine-containing components in the adhesive often bring adverse effects on occupational health and the environment, and no corresponding solutions are provided for the problem of the heat resistance stability of the impregnated layer.

[0006] Chinese invention patent CN117779453A discloses a non-phenolic environmentally friendly impregnation solution for fiber-reinforced materials. This solution can be used in both one-bath and two-bath impregnation processes, and its main components are sulfur-containing and reactive proton compounds. These sulfur-containing and reactive proton compounds can chemically bond with the epoxy or isocyanate active groups in the non-phenolic environmentally friendly adhesive resin, and simultaneously chemically bond with the rubber through sulfur bonds, enhancing the affinity between the impregnation layer and the rubber layer in the non-phenolic impregnation, thereby improving adhesive performance. This patented formulation avoids the addition of toxic and harmful substances such as phenols, making it more environmentally friendly and significantly improving adhesive performance. However, it does not mention improvements in the aging resistance and over-sulfurization degradation performance of the impregnation layer.

[0007] For example, Chinese invention patent CN117166252A discloses a two-bath impregnation solution for fiber skeleton materials. This method involves adding wetting and penetrating agents such as alkynyl alcohols to the first bath, allowing the latex to penetrate the fiber more quickly. Furthermore, adding a heat-resistant silane coupling agent to the first bath and a more heat-resistant inorganic fumed silica to the second bath improves the heat resistance of the second bath impregnation layer while simultaneously increasing the adhesion between the first and second baths. However, the penetration mechanism of alkynyl alcohols into the fiber is primarily chemical penetration combined with physical penetration. Due to the nucleophilic attack of the alkynyl group on the ester bond, local chemical bond breakage may occur, thus adversely affecting the mechanical properties of the fiber. Summary of the Invention

[0008] The purpose of this invention is to provide a first bath impregnation solution for two-bath impregnation, and to optimize the first bath impregnation solution to significantly improve adhesion and over-sulfurization degradation performance at a low cost.

[0009] The technical solution adopted by the present invention to solve the above problems is: the first bath impregnation solution for the two-bath impregnation method includes a dry component and a wet component, wherein the mass percentage of the wet component is 90%-99% and the mass percentage of the dry component is 1%-10%;

[0010] The dry components include the following components by mass percentage: 50%-75% blocked isocyanate component, 15%-40% epoxy component, 1-5% thioester antioxidant, 1-5% polyfunctional siloxane compound and 1-5% polyether compound.

[0011] Furthermore, the thioester antioxidant is a monoester or diester obtained by esterification reaction of one or more of thiodiacetic acid, dithiodiacetic acid, thiodipropionic acid, dithiodipropionic acid or dithiodibutyric acid with one or more of primary alcohols of C6 and below, secondary alcohols of C6 and below, monohydroxy polyethers or polyhydroxy polyethers.

[0012] Furthermore, the polyfunctional siloxane compound is an organosilicon compound containing one or more trifunctional siloxanes or two or more difunctional siloxanes.

[0013] Furthermore, the polyfunctional siloxane compound contains cross-linking active groups in the silicon-containing backbone or alkoxy moiety, including epoxy groups, isocyanate groups, blocked isocyanate groups, amino groups, mercapto groups, disulfide bonds, or polysulfide bonds.

[0014] Furthermore, the multifunctional siloxane compounds include one of Si69, Si75, KH550, KH560, KH590 and tetraethyl orthosilicate.

[0015] Furthermore, the polyether compound is a copolymer or homopolymer of monomer units such as ethylene glycol, propylene glycol, butanediol or glycerol, and the end-capping groups are one or more of hydroxyl, methoxy, ethoxy and glycidyl groups.

[0016] Furthermore, the epoxy component includes water-soluble or water-dispersible compounds of various epoxy monomers containing one, two or more epoxy groups, and mixtures of the above monomers.

[0017] Furthermore, the blocked isocyanate component includes a composition formed from one or more of toluene diisocyanate, diphenylmethane diisocyanate, and 1,6-hexanediisocyanate.

[0018] Furthermore, siloxane groups include alkoxy groups of C3 or below, monohydroxyalkoxy groups of C6 or below, and monohydroxy or polyhydroxy polyether groups with a main chain oxygen content of 25% or more.

[0019] Furthermore, the wet component includes water.

[0020] In summary, the present invention has the following advantages:

[0021] 1. This invention significantly improves the vulcanization adhesion and over-sulfurization degradation performance between fibers and rubber by adding thioester antioxidants, polyfunctional siloxane compounds and polyether compounds.

[0022] 2. The polyether compounds added in this invention act as penetrants to penetrate into the amorphous region of the cord, thereby penetrating and swelling the fibers and further enhancing the adhesive properties.

[0023] 3. This invention further improves the adhesion between fibers and rubber by leveraging the crosslinking activity of functional groups on the main chain of multifunctional siloxane compounds.

[0024] 4. The thioesters used in this invention are environmentally friendly and have good compatibility with the first bath adhesive solution. In addition, thioesters have good sulfur affinity and may react with the thiols at the ends of the rubber to form new sulfur bonds, thereby improving the aging resistance of the impregnation layer and enhancing the curing and adhesion properties of the rubber. Detailed Implementation

[0025] Based on the shortcomings of existing first-bath impregnation solutions as described in the background art, this embodiment discloses a first-bath impregnation solution for two-bath impregnation. This specific embodiment is merely an explanation of the present invention and is not intended to limit the present invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but as long as they are within the scope of the claims of the present invention, they are protected by patent law.

[0026] Specifically, the first bath of impregnation solution includes a dry component and a wet component, wherein the wet component accounts for 90%-99% by mass and the dry component accounts for 1%-10% by mass.

[0027] The dry components include the following components by mass percentage: 50%-75% blocked isocyanate component, 15%-40% epoxy component, 1-5% thioester antioxidant, 1-5% polyfunctional siloxane compound, and 1-5% polyether compound.

[0028] Furthermore, thioester antioxidants are monoesters or diesters of thiodiacetic acid, dithiodiacetic acid, thiodipropionic acid, dithiodipropionic acid, or dithiodibutyric acid. This can be understood as follows: the parent acid is thiodiacetic acid, dithiodiacetic acid, thiodipropionic acid, dithiodipropionic acid, or dithiodibutyric acid; the carboxylic acid group can undergo esterification with an alcohol to form an ester. A monoester is formed when one carboxylic acid group undergoes esterification to form an ester group, while a diester is formed when both carboxylic acid groups undergo esterification to form two ester groups.

[0029] Furthermore, thioester antioxidants are esters obtained by esterification of a parent acid with primary alcohols (C6 or less), secondary alcohols (C6 or less), monohydroxy polyethers, or polyhydroxy polyethers. Primary alcohols refer to alcohols with a hydroxyl group (-OH) attached to a primary carbon atom, including methanol (CH3OH), ethanol (CH3CH2OH), n-propanol (CH3CH2CH2OH), n-butanol (CH3(CH2)2CH2OH), n-pentanol (CH3(CH2)3CH2OH), and n-hexanol (CH3(CH2)4CH2OH). Secondary alcohols refer to alcohols with a hydroxyl group (-OH) attached to a secondary carbon atom, including isopropanol ((CH3)2CHOH) and sec-butanol (CH3CH2CH(OH)CH3). Primary or secondary alcohols with fewer than 6 C6 carbon atoms mean that the esterification product will be a compound in the form of monomethyl thiodipropionate, diethyl thiodipropionate, monosec-butyl dithiodipropionate, dimethyl thiodipropionate, dihexyl thiodipropionate, etc., i.e., esters of short-chain or medium-chain alcohols.

[0030] Furthermore, the multifunctional siloxane compound is an organosilicon compound containing one or more trifunctional siloxanes (R-Si-(OR)3) or two or more difunctional siloxanes (R2-Si-(OR)2). To ensure high reactivity and crosslinking ability, at least a trifunctional group is used, such as vinyltrimethoxysilane ((CH2=CH)Si(OCH3)3) or bis-γ-aminopropyltetramethoxydisiloxane (CH3O)3Si(CH2)3NH(CH2)2NH(CH2)3Si(OCH3)3. Alternatively, it may contain bifunctional groups, but at least two are required, such as bis-bifunctional siloxane monomers, including but not limited to 1,2-bis(dimethoxymethylsilyl)ethane ((CH3O)2(CH3)Si-CH2-CH2-Si(CH3)(OCH3)2), 1,2-bis(diethoxymethylsilyl)ethane ((C2H5O)2(CH3)Si-CH2-CH2-Si(CH3)(OC2H5)2), and 1,6-bis(dimethoxymethylsilyl)ethane. Hexane ((CH3O)2(CH3)Si-(CH2)6-Si(CH3)(OCH3)2), 1,4-bis(dimethoxymethylsilyl)benzene ((CH3O)2(CH3)Si-C6H4-Si(CH3)(OCH3)2); and linear polydimethylsiloxane or polyether siloxane oligomers containing bifunctional silane end groups, including but not limited to bis(dimethoxymethylsilyl)-terminated polydimethylsiloxane ((CH3O)2(CH3)Si-O-[Si(CH3)2O]_n-Si(CH3)(OCH3)2 (n ≥ 1)) and bis(dimethoxymethylsilyl)-terminated polyethylene glycol ((CH3O)2(CH3)Si-O-(CH2CH2O)_m-CH2CH2-O-Si(CH3)(OCH3)2).

[0031] Furthermore, polyfunctional siloxane compounds contain cross-linking active groups in their silicon-containing backbone or alkoxy group. These groups include epoxy groups, isocyanate groups, blocked isocyanate groups, amino groups, mercapto groups, disulfide bonds, or polysulfide bonds. The silicon-containing backbone refers to the organic groups directly attached to silicon atoms in the siloxane compound molecule. The common characteristic of these cross-linking active groups is that they can undergo chemical reactions under certain conditions to form covalent bonds. Their main function is to bridge the chemical bonds between the siloxane network, the fiber surface, other components in the impregnation solution, and the final rubber matrix. Epoxy groups, such as γ-epoxypropoxypropyltrimethoxysilane ((CH3O)CHCH2O(CH2)3Si(OCH3)3) and γ-epoxypropoxypropyltriethoxysilane ((CH2O)CHCH2O(CH2)3Si(OC2H5)3); isocyanate groups, such as γ-isocyanate-propyltriethoxysilane (OCN(CH2)3Si(OC2H5)3); blocked isocyanate groups refer to isocyanate groups that are blocked with phenol, caprolactam, oxime, etc. to protect and stabilize them in aqueous impregnation solutions, such as caprolactam-blocked γ-isocyanate-propyltriethoxysilane; amino groups, such as γ-aminopropyltriethoxysilane (H2N(CH2)3Si(OC2H5)3). 2H5)3), N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane (H2NCH2CH2NH(CH2)3Si(OCH3)3); mercapto groups such as γ-mercaptopropyltrimethoxysilane (HS(CH2)3Si(OCH3)3), γ-mercaptopropyltriethoxysilane (HS(CH2)3Si(OC2H5)3); disulfide or polysulfide bonds such as bis(triethoxysilylpropyl)disulfide ((C2H5O)3Si(CH2)3-SS-(CH2)3Si(OC2H5)3), bis(trimethoxysilylpropyl)tetrasulfide ((CH3O)3Si(CH2)3-S4-(CH2)3Si(OCH3)3).

[0032] Furthermore, the multifunctional silicon oxides include one of Si69, Si75, KH550, KH560, KH590, and tetraethyl orthosilicate.

[0033] Furthermore, the polyether compounds are copolymers or homopolymers of monomer units such as ethylene glycol, propylene glycol, butanediol, and glycerol, with end-capping groups of one or more of hydroxyl, methoxy, ethoxy, and glycidyl groups. Examples include polyethylene glycol, polyethylene glycol monomethyl ether, polyethylene glycol dimethyl ether, polyethylene oxide, polypropylene glycol, glycerol homopolymer, ethylene oxide-propylene oxide block copolymer, ethylene oxide-propylene oxide random copolymer, ethylene oxide-butanediol copolymer, and glycerol-initiated polyether.

[0034] Furthermore, the epoxy component includes various water-soluble or water-dispersible compounds containing one, two, or more epoxy groups, and mixtures of the above monomers. Examples include ethylene glycol glycidyl ether, polyethylene glycol monoglycidyl ether, polyethylene glycol diglycidyl ether, glycerol propoxylated diglycidyl ether, bisphenol A diglycidyl ether emulsion, bisphenol F diglycidyl ether emulsion, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, or a compound system formed by polyethylene glycol diglycidyl ether and glycerol triglycidyl ether (60:40), or a compound system formed by bisphenol F epoxy emulsion and phenolic epoxy emulsion (30:70).

[0035] Furthermore, the blocked isocyanate component includes compositions formed from one or more of toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and 1,6-hexamethylene diisocyanate (HDI). Examples include HDI-caprolactam adduct, HDI-methyl ethyl ketone oxime adduct, MDI-phenol blocking compound, and TDI-diethyl malonate prepolymer.

[0036] Furthermore, siloxane groups include alkoxy groups with C3 or fewer atoms, monohydroxy alkoxy groups with C6 or fewer atoms, and monohydroxy or polyhydroxy polyether groups with 25% or more oxygen in the main chain. Examples include methoxy (-OCH3), ethoxy (-OC2H5), propoxy (-OCH2CH2CH3), isopropoxy (-OCH(CH3)2), 2-hydroxyethoxy (-OCH2CH2OH), 3-hydroxypropoxy (-OCH2CH2CH2OH), 4-hydroxybutoxy (-O(CH2)4OH), 6-hydroxyhexyloxy (-O(CH2)6OH), polyethylene glycol monomethyl ether, polyethylene glycol, glycerol ethoxylate, and pentaerythritol polyether.

[0037] The following describes the two-bath impregnation solution preparation method used in the embodiments of this disclosure, specifically including:

[0038] Reagents:

[0039] Deionized water, sulfuric acid (CAS: 7664-93-9), tetrabutyl titanate (CAS: 5593-70-4), tetrahydrofuran (CAS: 109-99-9), anhydrous sodium sulfate (CAS: 7757-82-6), p-toluenesulfonic acid (CAS: 104-15-4), and toluene (CAS: 108-88-3).

[0040] Silane coupling agent, model KH550.

[0041] Ethylene glycol (CAS: 107-21-1), n-hexanol (CAS: 111-27-3), and polyethylene glycol 400 (PEG-400).

[0042] 3,3-Dithiodipropionic acid (CAS: 57757-57-0), thiodipropionic acid (CAS: 111-17-1) and dimethyl thiodipropionic acid (CAS: 4131-74-2).

[0043] Epoxy resin (model E-51) and blocked isocyanate dispersion (e.g., 50% by mass when dispersed in ethyl acetate).

[0044] instrument:

[0045] The apparatus includes a round-bottom flask, a distillation column, a distillation head, a vacuum receiving tube and receiving flask, a magnetic stirrer, an oil bath, a thermometer, a vacuum pump, and a rotary evaporator. All of these instruments are existing technologies required to meet the preparation methods of the embodiments of this disclosure. This disclosure does not impose further limitations on the specific models, capacities, and parameters of these instruments.

[0046] Reagent Preparation Example 1: Preparation of Hydrophilic Thioesters

[0047] 23.8 g of dimethyl thiodipropionate was weighed into a round-bottom flask, along with 24.8 g of ethylene glycol (4 equivalents) and 50 mg of tetrabutyl titanate. The flask was fitted with a spiked distillation column, a distillation head, a condenser, a vacuum receiving tube, and a receiving flask, and a magnetic stirrer was installed. After purging the flask with nitrogen, the mixture was heated to 80°C using an oil bath while stirring, and a vacuum was gradually created until reflux began. When the vacuum level reached approximately 50 kPa, byproducts began to be collected from the top of the distillation column. After continuing the reaction for 4 hours, the byproducts at the top of the column gradually disappeared.

[0048] After the reaction, the product was diluted with 100 ml of hot deionized water and coarsely separated while hot. 100 ml of tetrahydrofuran was added to the organic phase, dried with a small amount of anhydrous sodium sulfate powder, and filtered. The solvent was removed from the filtrate by rotary evaporation at room temperature to obtain thioester S1.

[0049] The above is only one of the preparation methods of thioester S1. It should be understood that those skilled in the art can adjust the above specific values ​​proportionally according to the specific mass of thioester S1 required.

[0050] Reagent Preparation Example 2: Preparation of Dithiodipropionic Acid Monoester

[0051] Weigh 21.07 g of 3,3-dithiodipropionic acid and 10.216 g of n-hexanol into a 100 ml round-bottom flask. Add 50 mg of p-toluenesulfonic acid and 50 ml of toluene, and heat until the toluene is refluxed. Use a water separator to remove water, and stop the reaction when the amount of water removed reaches 1.8 ml. After cooling, filter to remove unreacted dithiodipropionic acid. The resulting mixture is used as the dithiodipropionic acid monoester. Thioester S2 is obtained.

[0052] The above is only one of the preparation methods of thioester S2. It should be understood that those skilled in the art can adjust the above specific values ​​proportionally according to the specific mass of thioester S2 required.

[0053] Reagent Preparation Example 3: Preparation of Dithiodipropionic Acid Dipolyether Ester

[0054] Similar to reagent preparation example 1, polyethylene glycol (PEG-400) was used instead of ethylene glycol, and the PEG used had dihydroxyl end groups. No post-treatment was performed after the reaction, and the product was directly used in the adhesive formulation. Excess PEG-400 was included in the polyether components of the formulation. Thioester S3 was obtained.

[0055] The above is only one of the preparation methods of thioester S3. It should be understood that those skilled in the art can adjust the above specific values ​​proportionally according to the specific mass of thioester S3 required.

[0056] Reagent Preparation Example 4: Preparation of Polyether Siloxane Derivatives

[0057] Weigh 20g of silane coupling agent KH550 into a round-bottom flask, add 120g of PEG-400 and 100mg of sulfuric acid. Heat to 80℃ and react under vacuum for 3 hours until no more ethanol evaporates. The polyether siloxane derivative is obtained.

[0058] The above is only one of the preparation methods of polyether siloxane derivatives. It should be understood that those skilled in the art can adjust the above specific values ​​proportionally according to the required mass of the specific polyether siloxane derivative.

[0059] Two-bath impregnation solution preparation method:

[0060] First bath impregnation solution: See the examples and comparative examples below for details.

[0061] The second bath of impregnation solution comprises the following components by weight: 84 parts pure water, 3.4 parts resorcinol, 7.2 parts formaldehyde (37% formalin aqueous solution), 75 parts 40% butadiene-pyridine latex, and 5.6 parts 10% sodium hydroxide solution (pH 9.4).

[0062] Impregnation method:

[0063] The single-line impregnation process uses 1000D / 2, 450T / m polyester cord, and the cord surface has not undergone any special activation or washing treatment. The winding direction, temperature, and residence time on the impregnation machine are as follows: unwinding roller - first bath impregnation tank (room temperature, 5s) - first bath first oven (170℃, 4min), first bath second oven (245℃, 4min) - second bath impregnation tank (room temperature, 5s) - second bath first oven (170℃, 4min) - second bath second oven (245℃, 4min) - softener - take-up roller. During the impregnation process, the take-up softening tension is maintained at 5N, and the take-up speed is 4.5m / min. Furthermore, the specific temperature and tension settings in the impregnation area are shown in the table below: area Zone 1 Zone 2 Three Districts District 4 Fifth District District 6 Temperature / °C 170 245 / / 170 245 Cord tension during impregnation / N 7 7 6 6 9 5

[0064] General conditions for vulcanization testing:

[0065] The adhesive performance of the cords was evaluated using the CRA (Cord to Rubber Adhesion) peel test according to the Chinese national standard GB / T40725-2021, "Test Method for Peel Performance of Rubber-Dipped Cords to Rubber". Bridgestone-supplied test rubber was used. Six groups of cord samples (seven cords per group) were wound onto a mold, covered with rubber, and vulcanized at 160°C and a mold closing pressure of 2.45 MPa for 20 or 60 minutes.

[0066] The vulcanization test procedure is as follows: the middle 5 cords of each group of 7 cords are fixed to one side of the tensile testing machine, and the rubber is fixed to the other side of the tensile testing machine. The cords are then peeled off the rubber surface by stretching between the clamps. The adhesive performance is evaluated by the magnitude of the peel force and the amount of rubber covered by the peel surface.

[0067] The preparation of the first bath impregnation solution of the present invention will be specifically illustrated below with reference to the embodiments:

[0068] Example 1

[0069] Preparation of the first impregnation solution: Add 100 ml of deionized water to a beaker, set the stirring speed to 500 r / min, and add 3.73 g of epoxy resin while stirring. After the solution becomes clear, first add 0.28 g of Si75 and stir evenly, then add 0.14 g of polyethylene glycol dimethyl ether (M=250), and finally add 0.28 g of thioester S1. After stirring for 5 min, add 20.52 g of blocked isocyanate dispersion and continue stirring for 20 min. Then dilute with water to 400 g and stir for 5 min to obtain the first impregnation solution.

[0070] Example 2

[0071] Preparation of the first impregnation solution: Add 100 ml of deionized water to a beaker, set the stirring speed to 500 r / min, and add 3.73 g of epoxy resin while stirring. After the solution becomes clear, first add 0.28 g of Si69 and stir evenly, then add 0.14 g of polyethylene glycol monomethyl ether, and finally add 0.14 g of thioester S2. Continue stirring for 5 min, then add 20.52 g of blocked isocyanate dispersion and continue stirring for 20 min. Finally, dilute with water to 400 g and stir for 5 min to obtain the first impregnation solution.

[0072] Example 3

[0073] Preparation of the first impregnation solution: Add 100 ml of deionized water to a beaker, set the stirring speed to 500 r / min, and add 3.73 g of epoxy resin while stirring. After the solution becomes clear, first add 0.28 g of Si75 and stir evenly, then add 0.14 g of polyethylene glycol dimethyl ether (M=250), and finally add 0.14 g of thioester S3. After stirring for 5 min, add 20.52 g of blocked isocyanate dispersion and continue stirring for 20 min. Then dilute with water to 400 g and stir for 5 min to obtain the first impregnation solution.

[0074] Example 4

[0075] Preparation of the first bath impregnation solution: Add 100 ml of deionized water to a beaker, set the stirring speed to 500 r / min, and add 3.73 g of epoxy resin while stirring. After the solution becomes clear, add 0.28 g of Si75 and stir evenly. Then add 0.14 g of the self-made polyether siloxane derivative, and finally add 0.14 g of thioester S3. Continue stirring for 5 min, then add 20.52 g of blocked isocyanate dispersion and continue stirring for 20 min. Finally, dilute with water to 400 g and stir for 5 min to obtain the first bath impregnation solution.

[0076] Example 5

[0077] Preparation of the first impregnation solution: Add 100 ml of deionized water to a beaker, set the stirring speed to 500 r / min, and add 3.73 g of epoxy resin while stirring. After the solution becomes clear, add 0.28 g of Si69 and stir evenly. Then add 0.14 g of polyethylene glycol dimethyl ether (M=250), and finally add 0.14 g of thioester S2. Continue stirring for 5 min, then add 20.52 g of blocked isocyanate dispersion and continue stirring for 20 min. Finally, dilute with water to 400 g and stir for 5 min to obtain the first impregnation solution.

[0078] Example 6

[0079] Preparation of the first bath impregnation solution: Add 100 ml of deionized water to a beaker, set the stirring speed to 500 r / min, and add 3.73 g of epoxy resin while stirring. After the solution becomes clear, add 0.28 g of KH590 and stir evenly. Then add 0.14 g of polyethylene glycol dimethyl ether (M=250), and finally add 0.14 g of thioester S3. Continue stirring for 5 min, then add 20.52 g of blocked isocyanate dispersion and continue stirring for 20 min. Finally, dilute with water to 400 g and stir for 5 min to obtain the first bath impregnation solution.

[0080] Example 7

[0081] Preparation of the first impregnation solution: Add 100 ml of deionized water to a beaker, set the stirring speed to 500 r / min, and add 3.73 g of epoxy resin while stirring. After the solution becomes clear, add 0.28 g of Si75 and stir evenly. Then add 0.14 g of polyethylene glycol dimethyl ether (M=250) and finally add 0.14 g of thioester S1. Continue stirring for 5 min, then add 20.52 g of blocked isocyanate dispersion and continue stirring for 20 min. Finally, dilute with water to 400 g and stir for 5 min to obtain the first impregnation solution.

[0082] Example 8

[0083] Preparation of the first bath impregnation solution: Add 100 ml of deionized water to a beaker, set the stirring speed to 500 r / min, and add 3.73 g of epoxy resin while stirring. After the solution becomes clear, add 0.28 g of KH550 and stir evenly. Then add polyethylene glycol monomethyl ether, and finally add 0.14 g of thioester S1. Keep stirring for 5 min until the solution is uniform, then add 20.52 g of blocked isocyanate dispersion and continue stirring for 20 min. Finally, dilute with water to 400 g and stir for 5 min to obtain the first bath impregnation solution.

[0084] Example 9

[0085] Preparation of the first bath impregnation solution: Add 100 ml of deionized water to a beaker, set the stirring speed to 500 r / min, and add 3.73 g of epoxy resin while stirring. After the solution becomes clear, add 0.28 g of KH550 and stir evenly. Then add polyethylene glycol monomethyl ether, and finally add 0.14 g of thioester S2. Keep stirring for 5 min until the solution is uniform, then add 20.52 g of blocked isocyanate dispersion and continue stirring for 20 min. Finally, dilute with water to 400 g and stir for 5 min to obtain the first bath impregnation solution.

[0086] Example 10

[0087] Preparation of the first bath impregnation solution: Add 100 ml of deionized water to a beaker, set the stirring speed to 500 r / min, and add 3.73 g of epoxy resin while stirring. After the solution becomes clear, add 0.28 g of KH550 and stir evenly. Then add polyethylene glycol monomethyl ether, and finally add 0.14 g of thioester S3. Keep stirring for 5 min until the solution is homogeneous. Then add 20.52 g of blocked isocyanate dispersion, stir thoroughly, and dilute with water to 400 g while stirring. The first bath impregnation solution is obtained.

[0088] Comparative Example 1:

[0089] Preparation of the first bath impregnation solution: Add 100 ml of deionized water to a beaker, set the stirring speed to 500 r / min, and add 3.73 g of epoxy resin while stirring. After the solution becomes clear, add 20.52 g of blocked isocyanate dispersion and continue stirring for 20 min. Then, dilute with water to 400 g and stir for 5 min to obtain the first bath impregnation solution.

[0090] Comparative Example 2

[0091] Preparation of the first bath impregnation solution: Add 100ml of deionized water to a beaker, set the stirring speed to 500r / min, and while stirring, add 3.73g of multifunctional epoxy resin (such as commercially available trifunctional PY307-1). After stirring evenly, add 20.52g of blocked isocyanate dispersion, continue stirring for 20min, then dilute with water to 400g and stir for 5min. The first bath impregnation solution is obtained.

[0092] The formulations of the first bath impregnation solution in the above embodiments and comparative examples are shown in Table 1:

[0093] Table 1. Specific formulations of Examples 1-10 and Comparative Examples 1-2

[0094] The CRA test data for the above embodiments and comparative examples are shown in Tables 2 and 3:

[0095] Table 2. Adhesive properties of Examples 1-10 and corresponding Comparative Example 1

[0096] Table 3. Adhesive properties of Examples 1-10 and corresponding Comparative Example 2

[0097] Among them, CRA peel force represents the average peel force of 5 cords. The CRA peel surface rating method refers to the Chinese national standard GB / T 40725-2021 "Test method for peel performance of adhesive cords to rubber".

[0098] Comparison of CRA test data revealed that, compared with Comparative Example 1, the addition of thioester antioxidants, polyfunctional siloxane compounds and polyether compounds in Examples 1-10 resulted in varying degrees of improvement in the 20-minute or 60-minute vulcanization peel strength, enhancing the adhesion between fibers and rubber and the over-sulfurization degradation performance.

[0099] Examples 1-10 show that, compared with Comparative Example 2, the peel strength after adding thioester antioxidant, multifunctional siloxane compound and polyether compound was generally higher than that after 20 min or 60 min, further highlighting the synergistic effect of the three to significantly improve the adhesive performance, indicating that the effect of adding a single multifunctional epoxy on improving the adhesive performance is relatively limited.

[0100] Examples 1 and 7 compared the effect of the amount of thioester S1 added on the adhesive properties. When the amount of thioester S1 was doubled, both the adhesive properties and the over-sulfurization degradation properties were improved, indicating that appropriately increasing the amount of thioester added can improve the aging resistance of the fiber, which in turn is beneficial to improving the adhesive properties during vulcanization.

[0101] Examples 2 and 5 compared the effect of the type of polyether compound on the adhesive properties. Example 5 showed a slightly higher peel strength, and relatively better adhesive properties and oversulfurization degradation performance. Therefore, the number and position of the penetrating groups both have a certain influence on the peel strength. Multiple ether bonds in the middle position have a relatively better penetrating effect on the fibers and thus a higher peel strength.

[0102] Examples 3 and 4 improved the adhesion performance to varying degrees, with Example 4 showing a more significant improvement in the oversulfur degradation performance. This indicates that the multiple ether bonds in the middle position of the polyether siloxane derivative and the terminal hydroxyl groups generated by siloxane hydrolysis together improve the penetration of the fiber, further enhancing the adhesion performance.

[0103] Examples 3 and 6 compared the effects of multifunctional siloxane compounds Si75 and KH590 on adhesive properties, and Si75 showed relatively better adhesive properties, indicating that in addition to siloxane, the crosslinking activity of functional groups on the main chain of multifunctional siloxane compounds also affects adhesive properties.

[0104] Examples 8-10 compared the effects of different types of thioesters on adhesive properties. Their peel strength was significantly higher than that of Comparative Example 1, indicating that the three thioesters had varying degrees of effect on the anti-aging properties and improved adhesive performance of the impregnated layer. Example 10 showed relatively high peel strength because thioester S3 has a relatively high boiling point, resulting in less thermal volatilization loss during impregnation and higher functional durability during impregnation curing. Furthermore, the small amount of polyether component in thioester 3 further promoted fiber penetration.

[0105] The above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. The preferred embodiments have been described in detail. Those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the spirit and scope of the technical solutions of this application, and all such modifications and substitutions should be covered within the scope of the claims of this application.

Claims

1. A first bath impregnation solution for a two-bath impregnation process, characterized in that, It includes a dry component and a wet component, wherein the wet component has a mass percentage of 90%-99% and the dry component has a mass percentage of 1%-10%. The dry components comprise the following components by mass percentage: 50%-75% blocked isocyanate component, 15%-40% epoxy component, 1-5% thioester antioxidant, 1-5% polyfunctional siloxane compound and 1-5% polyether compound.

2. The first bath impregnation solution for two-bath impregnation according to claim 1, characterized in that, The thioester antioxidant is a monoester or diester obtained by esterification reaction of one or more of thiodiacetic acid, dithiodiacetic acid, thiodipropionic acid, dithiodipropionic acid or dithiodibutyric acid with one or more of primary alcohols of C6 and below, secondary alcohols of C6 and below, monohydroxy polyether or polyhydroxy polyether.

3. The first bath impregnation solution for two-bath impregnation according to claim 1, characterized in that, The polyfunctional siloxane compound is an organosilicon compound containing one or more trifunctional siloxanes or two or more difunctional siloxanes.

4. The first bath impregnation solution for two-bath impregnation according to claim 1, characterized in that, The polyfunctional siloxane compound contains cross-linking active groups in its silicon-containing backbone or alkoxy portion, including epoxy groups, isocyanate groups, blocked isocyanate groups, amino groups, mercapto groups, disulfide bonds, or polysulfide bonds.

5. The first bath impregnation solution for two-bath impregnation according to claim 1, characterized in that, The multifunctional silicon oxide compound includes one of Si69, Si75, KH550, KH560, KH590 and tetraethyl orthosilicate.

6. The first bath impregnation solution for two-bath impregnation according to claim 1, characterized in that, The polyether compound is a copolymer or homopolymer of ethylene glycol, propylene glycol, butanediol or glycerol as monomer units, and the end-capping groups are one or more of hydroxyl, methoxy, ethoxy and glycidyl groups.

7. The first bath impregnation solution for two-bath impregnation according to claim 1, characterized in that, The epoxy component includes water-soluble or water-dispersible compounds of various epoxy monomers containing one, two or more epoxy groups, and mixtures of the above monomers.

8. The first bath impregnation solution for two-bath impregnation according to claim 1, characterized in that, The blocked isocyanate component includes a composition formed from one or more of toluene diisocyanate, diphenylmethane diisocyanate, and 1,6-hexanediisocyanate.

9. The first bath impregnation solution for two-bath impregnation according to claim 1, characterized in that, The siloxane group includes alkoxy groups of C3 and below, monohydroxyalkoxy groups of C6 and below, and monohydroxy or polyhydroxy polyether groups with a main chain oxygen content of 25% or more.

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